1. Field of the Invention
The present invention generally relates to a substrate metallization method and, more specifically, to a method for forming a seed layer enabling the subsequent deposition of a metal.
2. Discussion of the Related Art
Components formed in integrated circuits are generally interconnected by means of metal tracks, for example, made of copper, formed at the surface of a substrate.
There exist many methods for forming such tracks. One of them is to perform an electroless deposition of copper on the substrate. An “electroless” deposition is an autocatalytic deposition performed without using electrodes.
Before performing an electroless deposition, it is necessary to form, on the substrate to be metalized, a seed layer which allows a good bonding on the substrate and which forms a seed for the autocatalytic reaction. Known methods for forming this type of seed layer carry out expensive operations, for example, series of operations of physical deposition, for example, physical vapor depositions (PVD), and etching operations, for example, plasma etchings. Further, several steps are generally necessary to form, on the one hand, a layer of a material ensuring the adherence to the substrate and, on the other hand, seeds of a material enabling the autocatalytic deposition of the metal. Generally, the material ensuring the bonding to the substrate is a material based on tantalum nitride (TaN) or on titanium nitride (TiN) and the material enabling the autocatalytic reaction of the metal is a material based on palladium (Pd), tin (Sn), and/or ruthenium (Ru). It should also be noted that a disadvantage of physical deposition methods is that many of them require substrate-by-substrate processings.